The objective of this project is to conduct, in accordance with the requirements of DHEW and UNM guidelines for research involving human subjects, the necessary studies required to evaluate the efficacy and potential benefit of negative pi mesons (pions) in treatment of advanced tumors, as follows: a. Human radiobiology studies to establish the relative biological effectiveness (RBE) of critical normal structures surrounding metastatic lesions by comparing dose response curves for pions and control x-radiation using sub-tolerance doses, b. Pilot studies to establish the response of primary tumors and surrounding normal structures to increasing doses of pions, and c. Phase III studies to establish the response of primary tumors and surrounding normal structures to curative doses of pions as compared to control x-radiation. Studies are being conducted as a joint project of the University of New Mexico Cancer Research and Treatment Center and the Los Alamos Scientific Laboratory, using pions produced at the Los Alamos Meson Physics Facility. Some 20 institutions throughout the nation will be sending patients to Los Alamos for pion therapy and entering patients in control studies at their home institutions.